RB N54 OEM PCV Vent Hose for Smooth Engine OperationThe OEM PCV Vent Hose acts as a check valve during low load operation, restriction the amount of filtered air (from the air filter on the rear induction turbo inlet) through the PCV Valve into the intake valves. Too little or too great of a restriction by the check valve hose can cause oil consumption issues during low load (high vacuum) engine operation. If the check valve does not open effectively the hose can also cause excessive crankcase